Air valve secondary carburetor



Sept. 13, 1966 H. A. CARLSON AIR VALVE SECONDARY CARBURETOR 2 Sheets-Sheet 1 Filed May 6, 1965 II II W flw m5 ML ER A HB I Q ATTORNEY Sept. 13, 1966 H. A. CARLSON AIR VALVE SECONDARY CARBURETOR 2 Sheets-Sheet 2 Filed May 6, 1965 FIG.3.

United States Patent 3,272,482 AIR VALVE SEKIONDARY CARBURETOR Harold A. Carlson, St. Louis, Mo., assignor to ACE lindustries, New York, N.Y., a corporation of New Jersey Filed May 6, 1965, Ser. No. 453,711 Claims. (Cl. 261--23) This invention relates to multi-stage, multi-barrel carburetors. In one of its aspects the invention relates to a multi-stage carburetor having an air valve in its secondary. In another of its aspects the invention relates to improved control of the secondary air valve operation. In still another of its aspects the invention relates to biasing means for the air valve of the secondary of the carburetor, which biasing is so modulated as to give the desired operating characteristics.

Automotive manufacturers and suppliers of component parts constantly strive to produce a vehicle with smooth and seemingly effortless performance. In line with this objective many of the newer models are equipped with larger engines with increased torque and improved drive trains and suspensions to better isolate engine and road vibration and sound. The purpose of such developments is to improve vehicle potential in the above respects. This invention is primarily intended to promote the full potential in this trend, and it is one of the objects of the invention to provide a carburetor better adapted in performance characteristics to obtain eflioiency and a throttle control for smoother engine response by an operator.

The first multi-barrel, multi-stage carburetors used on automobiles utilized primary and secondary barrels of about the same size. Because high cruising speeds were possible on operation of the primary barrels alone, the secondaries became useful only in the upper range of engine speeds and for this reason the added performance made possible by the secondaries had only limited utility. This fact was realized by some quite early, and attempts were made to modify these carburetors to bring the secondary in at lower speeds.

One approach to the earlier usefulness of the secondary barrels is to reduce the size of the primary and increase the size of the secondary, thus retaining the breathing capacity required by the larger engines. It is desirable and even necessary that the transition from primarythrottle-only operation to combine primary-secondary throttle operation be smooth and substantially free of any important change in air-fuel mixture such as would affect engine operation. In other words, at the time of transition the air-fuel mixture should not become excessively lean or excessively rich. Leanness of mixture can occur if fuel flow does not begin almost instantly with the cracking of the secondary throttle. I have now discovered that this undesirable result can be prevented by placing an air valve in the secondary barrel above the fuel nozzle and so controlling its operation as to insure the smooth transition from primary to secondary barrels.

Accordingly, it is an object of the invention to provide a multibarrel, multi-stage carburetor having a smooth transition from single-stage to multi-stage operation. It is another object of the invention to provide a carburetor having an air valve in the secondary barrel. It is still another object of the invention to provide control means for the air valve that will insure proper operation thereof.

In the drawing, FIG. 1 is a top-plan view of a carburetor constructed according to the invention.

FIG. 2 is an end view of the carburetor.

FIG. 3 is a sectional view of a carburetor according to the invention.

Referring to the drawing, a carburetor indicated erally at I is provided with a mounting tachment to the manifold of an engine genflange 2 for at- 3. An air horn 5 surmounts a cover plate 7 and, in addition to providing a passageway for air entry into the carburetor, also serves as a means for anchoring an air filter.

As shown, the carburetor is a four-barrel carburetor having a pair of primary barrels It and a pair of secondary barrels 12. types of multi-stage carburetors are adaptable to the invention and, for example, a two-barrel Inulti-stage carburetor having a single primary and a single secondary barrel would operate in the same manner. Primary barrel 10 is provided with a main venturi 14 and a smaller venturi 16 into which a main fuel nozzle 18 discharges fuel. Each primary barrel is also provided with an idle fuel system 20 having an idle fuel adjusting screw 22 as is customary in most conventional carburetors. Both the primary fuel nozzle 18 and the idle fuel system 20 are connected by suitable passageways to a fuel chamber containing a fioat-and-needle valve structure of conventional design.

Primary barrel It) is also provided with a throttle valve 25 mounted on a shaft 27 which is rotatably mounted in the body of the carburetor. The primary side of the carburetor is further provided with a choke 27 mounted on a shaft 29. As is customary, the choke is controlled by an automobile thermostatic control shown generally at 31. Connected to the shaft of automatic choke control 31 is a lever arm 33 which moves a link 35. Link 35 in turn moves an arm 37 which is attached to one end of a countershaft 39. Countershaft 3 moves choke shaft 29 by way of lever arms 41 and 43 through link 45.

Each of secondary barrels 12 is provided with a throttle plate 5t mounted on a shaft 52 which is rotatably journaled in the body of the carburetor. The secondary barrel is also provided with an air valve 54 mounted on a shaft 56. Fuel from a float chamber enters by way of passage 58 into a fuel well 60 from whence it passes to a nozzle 62. Fuel emerges from the nozzle by way of a plurality of small holes 64.

Primary throttle shaft 27 is actuated by means of a foot-pedal controlled rod which moves arm 70 to rotate shaft 27. This in turn moves arm 72 and, by way of link 74, arm 7 6 of the secondary throttle shaft 52. Arm 72 is not fixed directly to shaft 27 but instead is a loose lever rotatably mounted on shaft 27. Movement of arm 72 is accomplished as follows: Arm 77 is fixed to the end of shaft 27. Arm 77 is provided with a tab to which is hooked one end of a coil spring 73. The other end of spring 73 is hooked to a loose lever 71. Lever 71 is provided with a tab 78 adapted to contact a surface 79 of another loose lever 72. When shaft. 27 is rotated, arm 77 by way of spring 73 moves loose lever 71 and tab 78 (counterclockwise as seen in FIG. 2 When tab 78 contacts surface 79, arm 72 is rotated and this transmits force by way of link 74 to the arm 76 of secondary shaft 52, thus opening the secondary throttle 50. In the event the secondary is locked out, the: arm 77 continues to rotate but arm 71 does not move because spring 73 takes up the additional torque. The primary and secondary throttles are arranged to open sequentially. That is, the primary throttles rotate through approximately 60 degrees before the secondary throttle begins to open. From that time both throttles move together to arrive at the full open position at the same time.

Just before the secondary throttle begins to open, there is no air-flow through the secondary barrel and, of course, no fuel is flowing. It is desirable that, as the secondary throttle begins to open, fuel begins to flow at once and in the proper proportion of air and fuel. The air valve in the secondary above the secondary fuel nozzle assists in the initiation of fuel flow and in the maintenance of flow in the proper ratio. As will be explained later, the secondary air valve 54 is biased toward a closed position.

It is understood, of course, that other With the air valve closed, a partial opening of the secondary throttle will create a depression or lower pressure in the secondary barrel in the zone of the fuel nozzle, and this depression will initiate fuel flow through the nozzle. This same depression will then cause the air valve to open so that air and fuel will reach the intake manifold simultaneously and in the proper proportion. As the secondary throttle is opened wider, the greater demand for air causes the air valve to open wider and at that time there is acting upon the fuel nozzle the combined forces of a depression in the secondary barrel and the velocity of air passing over the fuel nozzle, and these two forces combine to draw fuel from the nozzle as required. The secondary air valve is mounted on its shaft 56 in an offcenter manner so that the pressure and velocity of air flowing through the barrel unite to force the air valve 54 open against the spring bias.

Referring to FIG. 2, it is seen that secondary throttle shaft arm 76 is provided with a side extension 76a and an opposite side extension 76b. Swivels 8t and 82 are secured to the respective extensions 76a and 76b. Secured to swivel 80 by a nut is a screw 84 having an eye for receiving a coil spring 86. Similarly, swivel 82 has secured to it a screw 88 having an eye for receiving spring 90. The other ends of spring 86 and 90 pass through an eye in lever arm 92 which is secured to the end of air valve shaft 56. Springs 86 and 90 are tension springs.

When throttle valve 50 of the secondary side is closed, a spring 86 biases air valve 54 towards its closed position, but spring 90 applies very little bias because of the geometry. As the secondary throttle is open (clockwise movement as seen in FIG. 2), tension on spring 86 is relaxed because the effective length of arm 76a is greater than the effective length of arm 92. At this same time the bias applied by spring 90 is increased as the arm 76b moves downwardly. Immediately following the initial opening movement of the secondary throttle valve, fuel will have started flowing through the nozzle 62 because of the depression in pressure and at the same time air valve 54 will have initiated opening movement because of the depression under the air valve and of atmospheric pressure above the air valve. As the throttle is opened wider, the pressure of air striking the air valve 54 causes it to open wider also. The effect of opening movement of air valve 54 is to rotate the arm 92 (counterclockwise, as seen in FIG. 2), thus stretching spring 90 to increase the bias applied by that spring.

The tension of springs 36 and 90 can be adjusted somewhat through adjusting the length of screws $4 and 88.

.Also, by proper selection of springs, the relationship between the biasing actions of the two springs can be varied over a wide range. For example, spring 86 could be relatively stiff and spring 90 much less so. With such an arrangement, the initial force required to open air valve 54 would be rather large, but once it was open part-way, the force required to make additional movement would be relatively smaller. A reverse arrangement, of course, is possible.

As will be appreciated by those skilled in the art, various modifications of the invention are possible. For example, a reversal of the geometry of the air valve biasing would permit the use of compression springs instead of the tension springs shown. It is also to be noted that lever arms 76a, 76b and 92 could be lengthened or shortened as desired. It is also to be mentioned that while the carburetor shown has smooth-bore secondary barrels, secondary barrels with venturis can be used where desired.

I claim:

1. A multi-stage carburetor comprising a body structure having a primary mixture conduit and a secondary mixture conduit for the flow of an air and fuel mixture therethrough, means including a primary nozzle for providing fuel flow into the said primary conduit, a secondary nozzle for providing fuel flow into the said secondary conduit, manually operable means including a primary throttle and a secondary throttle movably mounted respectively within said primary and secondary conduits and downstream respectively of said fuel nozzles for controlling the flow of air-fuel mixture therethrough, a control valve within said secondary conduit upstream of said secondary fuel nozzle, means eccentrically mounting said control valve for movement from a closed position and toward an open position by air flow through said secondary conduit, and spring biasing means for said control valve connected to said secondary throttle and responsive to the position of the secondary throttle whereby said control valve is urged into a closed position when said secondary throttle is in a closed position and the degree of bias exerted on said control valve is altered as said secondary throttle is opened.

2. The apparatus of claim 1 wherein said biasing means for said control valve comprises a lever arm connected to said control valve, a pair of lever arms connected to said secondary throttle, and a pair of tension springs connected at one end to the lever arm of the said control valve, and at their other ends to the said lever arms of the said secondary throttle.

3. Apparatus according to claim 1 wherein said manually operable means includes a control linkage for sequentially opening and closing said primary and secondary throttles.

4. The apparatus of claim 1 wherein said biasing means for said control valve comprises a pair of compression springs operatively linked to said secondary throttle valve.

5. A multi-stage carburetor comprising a body structure having a pair of primary mixture conduits and a pair of secondary mixture conduits for the flow of an air and fuel mixture therethrough, said primary conduits having a venturi restriction between the ends thereof, means including a different primary nozzle for providing fuel flow into the venturi restriction within each of said primary conduits, means including a different secondary nozzle for providing fuel flow into the said secondary conduits, manually operable primary and secondary throttles movably mounted respectively within each of said primary and said secondary conduits and downstream respectively of said primary and secondary nozzles, a choke valve positioned upstream of said nozzles in said primary conduits and adapted to provide choking action for both of said primary conduits, a control valve structure upstream of said secondary nozzles and adapted to control movement of air through both of said secondary conduits and spring-biasing means operatively connected to said control valve and to arms mounted on the shaft of said secondary throttle.

References Cited by the Examiner UNITED STATES PATENTS 2,832,576 4/ 1958 Henning.

3,186,691 6/1965 Manning.

FOREIGN PATENTS 1,371,397 7/1964 France.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Examiner. 

1. A MULTI-STAGE CARBURETOR COMPRISING A BODY STRUCTURE HAVING A PRIMARY MIXTURE CONDUIT AND A SECONDARY MIXTURE CONDUIT FOR THE FLOW OF AN AIR AND FUEL MIXTURE THERETHROUGH, MEANS INCLUDING A PRIMARY NOZZLE FOR PROVIDING FUEL FLOW INTO THE SAID PRIMARY CONDUIT, A SECONDARY NOZZLE FOR PROVIDING FUEL FLOW INTO THE SAID SECONDARY CONDUIT, MANUALLY OPERABLE MEANS INCLUDING A PRIMARY THROTTLE AND A SCONDARY THROTTLE MOVABLY MOUNTED RESPECTIVELY WITHIN SAID PRIMARY AND SECONDARY CONDUITS AND DOWNSTREAM RESPECTIVELY OF SAID FUEL NOZZLES FOR CONTROLLING THE FLOW OF AIR-FUEL MIXTURE THERETHROUGH, A CONTROL VALVE WITHIN SAID SECONDARY CONDUIT UPSTREAM OF SAID SECONDARY FUEL NOZZLE, MEANS ECCENTRICALLY MOUNTING SAID CONTROL VALVE FOR MOVEMENT FROM A CLOSED POSITION AND TOWARD AN OPEN POSITION BY AIR FLOW THROUGH SAID SECONDARY CONDUIT, AND SPRING BIASING MEANS FOR SAID CONTROL VALVE CONNECTED TO SAID SECONDARY THROTTLE AND RESPONSIVE TO THE POSITION OF THE SECONDARY THROTTLE WHEREBY SAID CONTROL VALVE IS URGED INTO A CLOSED POSITION WHEN SAID SECONDARY THROTTLE IS IN A CLOSED POSITION AND THE DEGREE OF BIAS EXERTED ON SAID CONTROL VALVE IS ALTERED AS SAID SECONDARY THROTTLE IS OPENED. 